Waxes have widely been used in a surface coated layer to impart an article with improved barrier properties, antiblocking properties, rub and mar resistance, controlled releasing properties, slip and lubricity, and water repellency. For example, waxes have been used as a surface finish on candies, chocolate bars, chewing gums and similar products; as an additive in polishes on furniture, leather, floor, automobile and fruits, as pharmaceutical coatings on pills, as a component in creams and lipsticks, as an additive in plastic film emulsions, carbon papers and inks, paints and varnishes, mold releases, metal casting, laminated cartons, water-proof compounds, and the like.
Aqueous wax dispersions of colloidal sizes (0.01 to 5 micron, typically from 0.01 to 1 micron) are generally known. Non-aqueous wax dispersions of colloidal sizes are difficult to prepare. Wax can be compounded into viscous non-aqueous media (viscosity greater than, for example, 1000 cps) by mechanical force. The problem with such an approach is that the particle size is difficult to predict and more difficult to reproduce. The resultant dispersions are not truly colloidal dispersions and on dilution wax particles will settle down or precipitate out.
Waxes are insoluble in most organic solvents, especially in polar organic solvents. Coatings can be made using highly toxic solvents such as propylene dichloride, which is on EPA P/U highly hazardous list.
It is well know in the art to incorporate wax in latex formulations. U.S. Pat. No. 4,569,896 teaches the production of a toner composition that includes resin particles of styrene methacrylate copolymer grafted or containing a low molecular weight wax plus a second resin composed of a terpolymer of styrene, acrylate and acrylonitrile. The developer also contains magnetite particles and carbon black. U.S. Pat. No. 5,034,454 describes the preparation of a crosslinkable water-dispersible acrylic copolymer wherein the polymerization is conducted in an organic solvent in the presence of a wax. The polymerization includes about 1 to 15 weight percent of a wax. U.S. Pat. No. 5,395,877 describes a process for the production of fortified vinyl latex rich in wax copolymerizing in an organic solvent in the presence of a wax under conditions to produce a low molecular weight resin. The copolymer is treated with ammonium hydroxide or aqueous alkali and used as a cosurfactant in a second aqueous emulsion polymerization of vinyl monomers to produce the fortified vinyl latex. U.S. Pat. No. 4,766,059 describes a method of making solid spherical beads having a mean size ranging form 0.5 to about 20 microns. The polymer beads contain a polymeric resinous material and a water insoluble wax. The process of making such solid beads involves the use of water miscible or immiscible low boiling solvent to dissolve both polymeric materials and wax, and subsequently removal of the solvent or solvent mixture by evaporation. This requires large processing equipment and lengthy processing time, which increases the expenses. U.S. Pat. No. 5,695,919 describes a lubricant impregnated core/shell polymer particle, the polymer particle comprising a core portion which is insoluble in the organic medium and a shell portion which has an affinity for both the core portion and the organic medium. It has also disclosed a procedure for preparing the lubricant impregnated particles. However, when the procedure is used to prepare a polymer shell containing a nonionic water soluble vinyl monomer, the resulted particle completely lost its affinity toward any organic solvent medium.
U.S. Pat. No. 4,608,401 describes a method of encapsulating in suspension in an aqueous medium discrete finely divided water-insoluble solid particles with a water-insoluble polymeric envelope comprising the steps of (1) suspending in an aqueous medium, under agitation milder than high shear mixing, (a) finely divided solid particles substantially free of ionic charges of such level that would cause flocculation upon subsequent initiation of addition polymerization and (b) a water-insoluble monomer capable of addition polymerization to form a water-insoluble polymer free of ionically charged groups, in the presence of (c) a water-soluble, non-ionic, surface-active stabilizing agent having a HLB number of at least about 13, the stabilizing agent being present in an amount sufficient to produce a generally stable suspension of the ultimately formed polymer encapsulated particles; (2) introducing an addition polymerization initiating agent which is not an anionic or cationic surface active or dispersing agent, and does not decompose to form same, in an amount sufficient to initiate addition polymerization of the monomer present; and, during or after the introduction of said initiating agent; (3) subjecting the resulting suspension to suspension polymerization conditions, while said suspension is maintained substantially free of anionic or cationic surface active or dispersing agents.
The objective of the present invention is to provide a process for the production of a non-aqueous composite wax particle dispersion which has predominately a wax phase and a polymer phase containing a compound free of ionic charge groups and capable of addition polymerization to form a water soluble homopolymer.